Specific aims: This randomized trial will assess the impact of epidural versus general anesthesia on cognitive and cardiac complications in a predominantly elderly population undergoing unilateral or bilateral primary total knee replacement. Secondly, this trial will document and comprehensively assess the incidence of persistent post-operative losses in cognitive function in an elderly population undergoing elective non-cardiac surgery. Thirdly, this study will test the reproducibility, validity, and responsiveness of a newly developed evaluative functional scale of cognitive performance in daily activities in this population. Experimental design and methods: A prospective randomized trial in predominantly elderly patients undergoing elective unilateral or bilateral total knee replacement assessing the effect of general versus epidural anesthesia on the outcomes of cardiac and cognitive complications. Baseline clinical and demographic data and comprehensive intra-operative monitoring data will be collected and analyzed. Occurrence of persistent deterioration of performance will be assessed in five cognitive domains of linguistic, psychomotor, attention, visuopatial, and memory function. Outcome will be measured by intrasubject comparison of psychometric test results three months post-operatively versus pre-operatively. Occurrence of major cardiac complications will be evaluated using a sensitive surveillance protocol to detect peri-operative myocardial infarction, pulmonary edema, pulmonary emboli and congestive heart failure. The administrator of the cognitive tests, the co-investigators assessing and reviewing post-operative cardiac outcomes, and the co-investigators reviewing and analyzing the cognitive test results will be blinded to the type of anesthesia intervention. Functional impact will be assessed with an evaluative scale administered pre-operatively and three months pre-operatively and three months post-operatively to both the patient and a close observer of the patient. The results of the functional scale will be correlated with the results of serial interpreted. Long term objectives: The long term objective is to prevent functionally significant post-operative cognitive complications, without a simultaneous increase in cardiac complications, in elderly patients undergoing elective surgery.